Recently, various wireless communication technologies are developing in accordance with the development of information communication technologies. As one of the various wireless communication technologies, a wireless LAN (WLAN) corresponds to a technology enabling a user to access the internet in wireless at home, a company or an area to which a specific service is provided using such a mobile terminal as a PDA (personal digital assistant), a laptop computer, a PMP (portable multimedia player) and the like based on a wireless frequency technology.
In order to overcome a limitation for the speed of communication, which is pointed out as a weak point of the wireless LAN, a recent technical standard has introduced a system in which network speed and reliability are enhanced and management distance of a wireless network is extended. For instance, IEEE 802.11n has introduced MIMO (multiple inputs and multiple outputs) technology using multiple antennas at both a transmitting end and a receiving end to support HT (high throughput) of which maximum data processing speed is faster than 540 Mbps, minimize a transmission error and optimize data speed.
In order to enable stations (STAs) supporting IEEE 802.11 system to support a fast initial link setup in IEEE 802.11 system MAC (medium access control) layer, a new standard is developing as IEEE 802.11ai. For instance, an object of the IEEE 802.11ai is to provide a technology supporting a fast link setup in a situation that a huge number of users are getting out of a previously connected wireless LAN coverage and practically accessing a new wireless LAN at the same time for a case of transferring a public transportation and the like. And, main characteristics of the IEEE 802. 11ai can be summarized as a security framework, IP address assignment, fast network discovery and the like.